In the prior art, Patent Document 1 discloses a perfluoropolyether based gel composition comprising a linear perfluoropolyether compound containing at least two alkenyl groups per molecule and having a perfluoropolyether structure in its backbone, a linear perfluoropolyether compound containing one alkenyl group per molecule and having a perfluoropolyether structure in its backbone, an organosilicon compound having at least two hydrosilyl groups per molecule, and a hydrosilylation reaction catalyst. The composition cures into a gel having a good profile of heat resistance, chemical resistance, solvent resistance, water/oil repellency, and weatherability.
This perfluoropolyether based gel composition performs well in most applications. However, in some applications including sealing agents for use in semiconductor fabrication equipment, sealing and potting agents for use with engine oil, sealing and potting agents for use in engine exhaust system parts, not only chemical resistance, but also acid resistance is needed.
Patent Document 2 describes a polymer having a terminal structure in the form of [aromatic ring-silicon atom-vinyl group] structure. The polymer is fast curable owing to the [silicon atom-vinyl group] structure, the bond site between aromatic ring and silicon atom is known to be vulnerable to acid. On the other hand, polymers whose terminal structure is free of [aromatic ring-silicon atom-vinyl group] structure, for example, a polymer having a terminal structure in the form of [aromatic ring-alkylene group-vinyl group] structure and a polymer having a terminal structure in the form of [amide group having aromatic ring substituent group on side chain-alkylene group-vinyl group] structure (see Patent Documents 3 and 4) have good acid resistance, but lack fast cure. In terms of acid resistance, the polymers whose terminal structure is free of [aromatic ring-silicon atom-vinyl group] structure are good in resistance to sulfuric acid, but short in resistance to nitric acid. Since the engine exhaust system parts mentioned above are exposed to not only SOx, but also NOx in the exhaust gases, they must have high nitric acid resistance. It is thus desired to have a perfluoropolyether based gel composition having a good profile of oil resistance, chemical resistance, and acid resistance, specifically resistance to both sulfuric acid and nitric acid.